Tuesday, April 30, 2013

Storyteller and listener: an ongoing dynamic interaction between two brains

One of the points I strive to make when I'm teaching writing is that though the words on the page flow from the story in the writer's head, the words on the page aren't the story, but the means through which readers can imagine and re-create the story in their heads. Writers notice when the stories they've created differ from those re-created by readers more than they do the congruences-- presumably because we take the latter for granted and tend to assume that if we and our readers are both doing what we should, there ought not to be many differences between the created and re-created stories. Maybe that assumption is just hopeless wishful thinking. After all, the reasons for those discrepancies are many and many, not necessarily the fault of either side.

Given my longtime preoccupation with this relationship, I'm fascinated to find that neuroscientists are comparing, via fMRI, what happens in the brains of people telling a story with those hearing it. One attempt at such a comparison is the paper Speaker-listener neural coupling underlies successful communication, published in the Proceedings of the National Academy of Science (July 26, 2010) available (free) online, by Greg J. Stephens, Lauren J. Silbert, and Uri Hasson.(One of the lovely features of this online publication is that rolling the cursor over hyperlinks will bring up figures and references without the user having to click away from the page to see them.)

I especially like that the authors characterize communication as an "ongoing dynamic interaction between two brains." Would it astonish you to learn that the authors report that the brains
of those hearing a story mirror-- usually with a one-to-three-second
delay-- what happens in the brains of the person telling the story? (Though of course once I start thinking about it, I have to wonder to what extent the brains of persons engaged in antagonistic communication might mirror one another.) The authors suggest that this "neural coupling resembles the action/perception coupling observed within mirror neurons." Particularly interesting for writers is that those listening to stories do a certain amount of anticipating-- and that the more their brains anticipate, the greater their comprehension of the story communicated:

Our analysis also identifies a subset of brain regions in which the activity in the listener's brain precedes the activity in the speaker's brain. The listener's anticipatory responses were localized to areas known to be involved in predictions and value representation (20–23), including the striatum and medial and dorsolateral prefrontal regions (mPFC, dlPFC). The anticipatory responses may provide the listeners with more time to process an input and can compensate for problems with noisy or ambiguous input (24). This hypothesis is supported by the finding that comprehension is facilitated by highly predictable upcoming words (25). Remarkably, the extent of the listener's anticipatory brain responses was highly correlated with the level of understanding (Fig. 4B), indicating that successful communication requires the active engagement of the listener (26, 27).

I've long believed that the stories that are least likely to be grossly misread are those that are in important ways already familiar to readers. Intelligibility is all about familiarity-- which is why it's so difficult for writers to get good readings for new, unfamiliar-to-the-reader stories.
A more recent study conducted at Emory--reported here looked at how the brain reacts to metaphors:

"We see that metaphors are engaging the areas of the cerebral cortex involved in sensory responses even though the metaphors are quite familiar," says senior author Krish Sathian, MD, PhD, professor of neurology, rehabilitation medicine, and psychology at Emory University. "This result illustrates how we draw upon sensory experiences to achieve understanding of metaphorical language."

Sathian is also medical director of the Center for Systems Imaging at Emory University School of Medicine and director of the Rehabilitation R&D Center of Excellence at the Atlanta Veterans Affairs Medical Center.

Seven college students who volunteered for the study were asked to listen to sentences containing textural metaphors as well as sentences that were matched for meaning and structure, and to press a button as soon as they understood each sentence. Blood flow in their brains was monitored by functional magnetic resonance imaging. On average, response to a sentence containing a metaphor took slightly longer (0.84 vs 0.63 seconds).

In a previous study, the researchers had already mapped out, for each of these individuals, which parts of the students' brains were involved in processing actual textures by touch and sight. This allowed them to establish with confidence the link within the brain between metaphors involving texture and the sensory experience of texture itself.

"Interestingly, visual cortical regions were not activated by textural metaphors, which fits with other evidence for the primacy of touch in texture perception," says research associate Simon Lacey, PhD, the first author of the paper.

"I don't think that there's only one area responsible for metaphor processing," Sathian says. "Actually, several recent lines of research indicate that engagement with abstract concepts is distributed around the brain."

"I think our research highlights the role of neural networks, rather than a single area of the brain, in these processes. What could be happening is that the brain is conducting an internal simulation as a way to understand the metaphor, and that's why the regions associated with touch get involved. This also demonstrates how complex processes involving symbols, such as appreciating a painting or understanding a metaphor, do not depend just on evolutionarily new parts of the brain, but also on adaptations of older parts of the brain."

All of which underscores the importance of using sensory detail in fiction, no? (And probably in nonfiction, as well-- whenever possible.)

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